I've had the WD My Book essential now for about a month. I got the 250GB version, but it's only got a 2mb cache. For a backup drive I couldn't fault it. Seems pretty quick, is quite and isn't hot.

Looks pretty nice with a button at the front so it's easy to turn on and off. I just let mine boot up with the pc and shutdown with the pc. I wouldn't know it was there apart from the extra storage space.

The only slight issue I had was that it was preformatted to FAT32. That wasn't a problem though. I plugged it in, straight away the 'Found new hardware' popped up and it was installed in seconds. Appeared in Explorer straight away so I just right clicked and chose format. Chose the NTFS system and let it do it's thing. An hour later it was ready and it's been faultless since.

My dad had an external hard drive (200gb) and i dropped an iron on it. I know that was stupid, but the USB connection broke inside.

I opened it up, and low and behold, guess what I found? A regular Western Digital hard drive with a SATA cable going to a controller board to change the signals to USB and Firewire, and being sold by Lacie for a higher price.

I also find out, that its actually cheaper to buy an internal hard drive, and buy a external case for it, which changes it into USB/firewire.
The case would only cost you about £15-£20 extra, to change any drive, and thats alot cheaper, than going for a make that'll charge you triple that to do the same thing.
They are widely available, and you'll save ALOT of money in doing so.

Well, that's actually better that they have a normal internal hdd in there... it's better overall, besides the price. What about Seagate?

In addition, I probably wouldn't be able to make myself an external hdd... and I'd like an external.
^In response to Kage

I would go with the Seagate, because not only is it a second hard drive that you can put your data on, it also doubles as a backup drive to back up your primary drive. That, in itself, would come in handy for me, because I have experienced my computer crashing before and having to rebuild. One reason why I invested in Ghost.